1. Field of the Invention
The present invention relates to a current balancing apparatus, a current balancing method, and a power supply apparatus, for balancing currents passing through a plurality of loads connected in parallel.
2. Description of the Related Art
An example of an apparatus for supplying power to a plurality of loads is an apparatus for lighting a plurality of LEDs (Light Emitting Diodes) disclosed in Japanese Unexamined Patent Application Publication No. 2003-332624 (Document 1).
FIG. 1 illustrates the LED driving apparatus disclosed in Document 1. The apparatus has a DC power source Vdd, a step-up circuit 27, LEDs 21 to 26, sink drivers 12 to 14, bypass units 15 to 17, and a selector 18. The sink drivers 12 to 14 turn on/off in response to time division signals S1 to S3. Each of ends of the sink drivers 12 to 14 is connected to related one of terminals P23 to P25 each connected to the LEDs 21 to 26. The bypass units 15 to 17 are connected in parallel with the sink drivers 12 to 14 and pass currents when the sink drivers 12 to 14 are OFF, the currents being small not to make the LEDs 21 to 26 emit light.
The selector 18 detects a drain-source voltage of one of the sink drivers 12 to 14 and a current passing through one of the three lines of the LEDs 21 to 26 and controls an output voltage from the step-up circuit (converter) 27.
According to this related art, the sink drivers 12 to 14 pass necessary currents through the LEDs 21 to 26 during a period of lighting the LEDs 21 to 26. During a period of not lighting the LEDs 21 to 26, the sink drivers 12 to 14 stop the currents and the bypass units 15 to 17 bypass small currents, to prevent an output voltage from the converter 27 from jumping up.
Other related arts are disclosed in, for example, Japanese Unexamined Patent Application Publications No. H11-67471 and No. 2002-8409.